The connection of wind turbines to electricity distribution networks, as well as the use of such turbines as a means of supply for electrical machinery, creates specific problems in comparison to other sources of energy. Different solutions have been proposed for these problems.
One of such problems is the production of a short circuit in the network, causing the connection of the wind farm to change. To this respect, patent DE 10206828 proposes a control system to detect this short circuit, disconnecting the network from the wind turbine park which, without ceasing operation, has the means to dissipate and accumulate the energy produced until it can be reconnected to the network once the short circuit has been repaired.
Another problem is that of an over-voltage in the network, potentially affecting the wind turbine park. Patent DE 10105892 proposes a system to detect this problem and to create a solution, dissipating the excess energy produced in the form of heat.
Patent DE 19624809 proposes a filtration system in the alternative network itself to obtain a specific wave signal through the variation in rotor turning speed of an electric generator.
Finally, patent U.S. Pat. No. 5,127,085 limits or eliminates damaged currents in the alternative network which could cause a voltage surge in internal alternator components.
This last technique, however, does not address the problem caused by “voltage sags”.
Sudden voltage steps can be caused in the connection to the electrical output network of a park of electric generators such as wind turbines, as a result of network defects. In such cases, implementing the proper protection disconnects the defective part of the network, producing a new voltage step in the opposite direction and restoring the voltage to the regular level, prior the defect. The combination of both steps is known as a “voltage sag” which can be defined by two parameters: both the magnitude and the duration of the voltage step.
A “voltage sag” can cause a wind turbine park to disconnect from a network, consequentially having damaging effects on the management of the network itself. Voltage steps also damage wind turbine operation as they cause a sudden change in voltage torque, affecting multiplier life. It is thus desirable to have the procedures and devices that can prevent these effects. The present invention offers a solution to that demand.